The invention relates to a circuit arrangement for the drive of a vehicle.
In known drives for motor vehicles, in particular for rail vehicles in underground operation, as drive source an internal-combustion engine is employed, possibly an exhaust-purified diesel engine, which acts via a multistage change-speed gear on one, preferably two, drive axles. With a change-speed gear it is not possible to avoid wheel slip, in particular with rail vehicles, and obtain adequate acceleration values.
For driving motor vehicles hydrostatic machines are also known which are connected to a conduit with impressed pressure, i.e. in which a predetermined pressure is maintained. The hydrostatic machines are units of variable absorption or displacement volume, the adjustment means of which is adjustable beyond the zero point in both directions and which therefore in both directions of rotation drive a load in motor operation or in pump operation or driven by the load; in the latter case fluid can be conveyed back into the conduit and thus a hydraulic accumulator charged. By means of the setting of the adjustment means of the hydrostatic machine, which is done via a speed control circuit and possibly a position control circuit, the absorption or displacement volume of the machine and thus the torque furnished or taken up by said machine is set. Corresponding to the load conditions a speed of rotation arises which is fed back to the speed control circuit as actual value. The reference or desired value for the speed can be selected in a drive switch, the forward-reverse direction for the vehicle being governed by the polarity of the desired value signal whilst for the acceleration or retardation of the vehicle the amplitude of the desired value voltage is correspondingly increased or decreased.
Proceeding from such a hydrostatic drive, which is also referred to as secondary controlled drive because the machines are connected to the pressure network with impressed pressure and the control thus takes place secondarily, the problem underlying the invention is to further develop the drive of a vehicle having at least one driven axle so that optimum acceleration and retardation operations are possible and wheel slip is avoided irrespective of the particular load conditions occurring and the particular wheel grip.